Scientific Forecaster Discussion
fxus62 kgsp 150555
Area forecast discussion
National Weather Service Greenville-Spartanburg SC
1255 am EST Fri Nov 15 2019
a surface low pressure center will move from the northeast Gulf of
Mexico to the coastal waters of the Carolinas tonight through
Friday. The system will linger along the southeast coastline through
Saturday before moving away to the northeast on Sunday. A series of
troughs of low pressure will then move through the region during the
early to middle part of next week, with the strongest of these
crossing the area in the Tuesday to Wednesday timeframe.
Temperatures will remain below normal for the next week, but
Near term /through today/...
as of 1250 am: a broad deformation zone of light rain continues to
press into the region from the southwest. This is expected to pivot
across the I-85 corridor and points southeast through much of today.
Have tweaked the ongoing forecast mainly for aviation interests.
The pattern will continue to amplify over tonight as a southern
stream upper trof digs down across the arklatex region and pushes
towards the Gulf Coast by tomorrow morning. As it does, it will
become a closed low and continue to push southeast thru day. By tomorrow
night, the upper low will be centered just to our south-southwest over the
Florida Panhandle. At the sfc, southwesterly moist upglide will continue to
deepen ahead of the Gulf disturbance. The disturbance will organize
into a closed sfc low by early Friday morning as it moves over
central Florida. Broad sfc high pressure to our north and west, will
keep low-lvl winds northerly to north-northeasterly and ample cloud cover over the fcst
area thru tomorrow. Rain showers will gradually increase in coverage
thru the evening and into the overnight. The northerly flow will pull
drier low-lvl air across roughly the northern half of the County warning forecast area and
help to limit precipitation over those areas. All precip should be
rain with the exception of some light snow showers possible across
the northern mtns tonight. Between a quarter to a half inch of quantitative precipitation forecast
is possible across our southernmost zones thru tomorrow, with less
expected the farther north you go. Ample cloud cover will help keep
lows temps at least 10 degrees warmer overnight, but they will still
be a few degrees below normal for mid-November. Temps tomorrow will
remain well-below normal, with highs only reaching the low 50s
across the lower terrain and upper 40s across the higher terrain.
Short term /tonight through Sunday/...
as of 210 PM thursday: the closed 500 mb low center passing just to the
south of the forecast area will move across southern Georgia Friday
night and over the adjacent Georgia coastal waters through Saturday.
Depending on the eventual strength of the low, deformation zone
forcing may be slow to clear the area through Saturday. Will thus
keep chance pops going through at least 18z for the southeast
Piedmont. Fortunately, surface temperatures and profiles look
sufficiently warm for mainly liquid ptypes, although a few western
NC areas could see a brief flurry as the precipitation is ending.
Shortwave ridging will develop over the forecast area for the latter
half of the weekend, but with additional troughing developing over
the central Continental U.S. On Sunday. Anticipate dry and cool weather, with
temperatures running at least 5 to 10 degrees below climo.
Long term /Sunday night through Thursday/...
as of 215 PM thursday: confidence is relatively high that various
shortwaves/trough axes will move through the eastern U.S. During the
early to middle part of next week. However, confidence is much less
on the specific timing of these features, and the associated periods
of greatest forcing and moisture.
Both the GFS and European model (ecmwf) bring a negatively tilted trough across the
southern Appalachians Sunday night into Monday, but with very
limited moisture return. The sharpest trough or vorticity lobe may
cross the region on Tuesday or Wednesday as a clipper-type system
moves through the eastern longwave trough. Will feature the best
pops with this latter system, but confine to the chance range or
less. Temperatures could be sufficiently cold Tuesday night to
warrant a brief rain/snow mix, especially along the higher
elevations of the NC mountains, and possibly north of I-40 across
the foothills. Drying, deep-layer northwesterly flow should then
set back up behind the departing trough axis on Thursday.
Aviation /06z Friday through Tuesday/...
at kclt and elsewhere: below normal confidence in 06z tafs
especially for along the I-85 corridor including kclt as cigs may
bounce back and fourth between low MVFR and VFR through 15z and
again after 00z. The region will be on the backside of a developing
coastal low, supporting periods of rain and MVFR/IFR cigs. Drier low
level air wrapping behind the system should support generally VFR
cigs/vsbys with limited rain to northern areas including kavl and
khky. There is a 30 percent chance that heavier bands of rain and
gusty winds wrap back into the I-77 corridor including kclt towards
the end of the taf period.
Outlook: precipitation and flight restrictions will likely linger
into the weekend, especially along and southeast of I-85 corridor,
as the aforementioned coastal low drifts up along the coast.
06-12z 12-18z 18-24z 00-06z
kclt high 91% high 100% high 96% high 100%
kgsp high 94% high 100% high 98% high 100%
kavl high 100% high 100% high 100% high 100%
khky high 100% high 100% high 100% high 100%
kgmu high 93% high 100% high 99% high 100%
kand high 85% high 91% high 85% high 100%
The percentage reflects the number of guidance members agreeing
with the scheduled taf issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link: